Investigations on laser bending of a two-ply clad sheet and its microstructural evolution

Abstract

The effectiveness of the laser forming process is strongly dependent on the interaction of thermal and mechanical properties inherent in a clad sheet comprising different layers having different properties. The present research examines how laser power, scanning speed, and number of passes at two distinct levels of maximum and minimum affect the bend angle in the samples of a two-ply clad sheet comprising SS430 and AA1050 layers. The clad sheet, was chosen because of its demand in precision manufacturing for performance attributes like as corrosion resistance, thermal conductivity, and mechanical strength. A central composite design was carried out to determine the correlation between the input variables and output response. Design-Expert software was employed to design the experiments, which gave 20 runs to conduct the tests. Response surface methodology was incorporated to optimize the results. The results obtained by analysis of variance were found to be in agreement with the results obtained by experiments. An optimized combination of 0.917 kW laser power, with number of scans and velocity of 63 and 33 mm/s, respectively resulted in a maximum bend angle of 39° with a relative error of 2.14%. The effect of laser bending due to multiple scans on the clad sheet along the laser path in the thickness direction was also examined to understand the microstructure and texture evolution by electron backscattered diffraction technique. The irradiated surface is affected the most and the texture becomes poor whereas, the layer of AA1050 below the irradiated surface improved in texture. It is also observed that the residual stress in the innermost layer of SS430 is of compressive nature whereas the stress in the outermost layer of AA1050 is tensile in nature.